One of the Dark Angels Legion's six "wings", the Dreadwing detachment existed for a single, focused purpose: extermination.
The formation was deployed only when it was deemed necessary to carry out the complete and total annihilation of a target. These specialists employed forgotten technologies, superheavy armor, weapons of mass destruction and worse to wipe designated areas from the face of the galaxy. "Scorched earth" would only begin to describe the utter devastation left in the passing of the Dreadwing. They were prepared to use napalm, nerve gas, nuclear fire, phosphex and anything else that could be found in the darker depths of the Legion armories. Nothing less than the complete destruction of the enemy and everything around him would be deemed satisfactory in after-action reports.
During the Horus Heresy, primarch Lion El'Jonson deployed his Dreadwing on Macragge to quell rebellions on the planet. The Dark Angels operations resulted in untold devastation and collateral damage, and primarch Guilliman of the Ultramarines was slightly miffed.
When the Dreadwing marched to war, their doomed foes were treated to a chilling, never-ending battle chant: WE HAVE COME, WE ARE DEATH.